lodash/test/isError.spec.ts

import assert from 'node:assert';
import lodashStable from 'lodash';

import {
    errors,
    stubTrue,
    CustomError,
    falsey,
    stubFalse,
    args,
    slice,
    symbol,
    realm,
} from './utils';

import isError from '../src/isError';

describe('isError', () => {
    it('should return `true` for error objects', () => {
        const expected = lodashStable.map(errors, stubTrue);

        const actual = lodashStable.map(errors, (error) => isError(error) === true);

        assert.deepStrictEqual(actual, expected);
    });

    it('should return `true` for subclassed values', () => {
        assert.strictEqual(isError(new CustomError('x')), true);
    });

    it('should return `false` for non error objects', () => {
        const expected = lodashStable.map(falsey, stubFalse);

        const actual = lodashStable.map(falsey, (value, index) =>
            index ? isError(value) : isError(),
        );

        assert.deepStrictEqual(actual, expected);

        assert.strictEqual(isError(args), false);
        assert.strictEqual(isError([1, 2, 3]), false);
        assert.strictEqual(isError(true), false);
        assert.strictEqual(isError(new Date()), false);
        assert.strictEqual(isError(slice), false);
        assert.strictEqual(isError({ a: 1 }), false);
        assert.strictEqual(isError(1), false);
        assert.strictEqual(isError(/x/), false);
        assert.strictEqual(isError('a'), false);
        assert.strictEqual(isError(symbol), false);
    });

    it('should return `false` for plain objects', () => {
        assert.strictEqual(isError({ name: 'Error', message: '' }), false);
    });

    it('should work with an error object from another realm', () => {
        if (realm.errors) {
            const expected = lodashStable.map(realm.errors, stubTrue);

            const actual = lodashStable.map(realm.errors, (error) => isError(error) === true);

            assert.deepStrictEqual(actual, expected);
        }
    });
});